Issues with Pointiness
It is important to note that booleans do not generally make clean quad-based topology. Therefore, no matter how high topology you go, you'll generally get tris and even sometimes n-gons that can destroy an otherwise passable result. Pointiness needs to rely on vertex data, and it seems that the model was nowhere near high poly enough to look clean with the pointiness node. (matching the topology density of the boolean and base model can help somewhat).

Because it's vertex based, the program can only really check if the vertex is bent, or the angle of its sides and other quads. this means the pointiness node will look up to 2 vertices away from any given point of measurement. The best way to combat this, is to make sure it always looks just as far, no matter what direction it tries. That's accomplished, normally, with retaining loops.

Your model may be high poly, but there will always be vertex-sized artifacts in the texture if you make it using vertex data on bad, or even normal but booleaned topology. you can only make them smaller.

there are only a few ways to deal with this in a boolean workflow:


brute forcing geometry density to millions of vertices.
retopology, to make proper retaining loops manually or via some remesh algorithm
wait until modeling is over, and paint the area by hand without baking textures
use a very low poly boolean object, so you barely have to work to retopologize just the area around the booleaned geometry.


The boolean workflow is nice, fast, and easy on the eyes, but when it comes to topology it's just about the most notoriously inadequate workflow. I would personally tell you to manually retopologize the part after if you absolutely must use pointiness to texture it, and if you do, you should probably use this proven topology, it's a favorite among hard surface modellers:

this is what you have, simply subdivided then booleaned


but if you just cut a low poly hole and put some nice loops around it to tell it where the curve is...



it ends up like this, with only a few polys, with the help of the subdiv modifier! (ignore the creases, I was too lazy to put retaining loops on the cube other than the hole)



buuuut I've gotta say I wouldn't suggest using pointiness other than as something to mix with a noise texture, so that I can get some nice paint chipping or grime on corners as such: